Conventionally, there is well known a PLC system provided with a programmable indicator that is a PLC (Programmable Logic Controller) or a HMI (Human Machine Interface).
For example, JP 2012-208931 A discloses a configuration for a PLC system including a PLC that controls operation of a device and a personal computer that is a maintenance device connected to the PLC through a communication line to perform maintenance of the PLC.
The PLC includes an information storage unit in which information on an operating state of the PLC is stored, the information being directly recognizable by a user, and a PLC information storage unit. When a predetermined operating state of the PLC is detected, the PLC information storage unit stores PLC information corresponding to the operating state of the PLC in an abnormal generation information storage region from pieces of information stored in the information storage unit. The personal computer includes a PLC information acquisition unit that acquires the PLC information stored in the PLC information storage unit and an information display unit that displays the PLC information acquired from the PLC information acquisition unit.
In JP 2012-208931 A, “because a time lag is not generated between the operating state of the PLC and the information, the information acquired from the PLC side can directly be displayed on the maintenance device side” is described as an effect of the PLC system having the above configuration.
For example, JP 2013-222356 A discloses a human-machine screen display method for a plant monitoring control device. A display in which a plurality of screens are displayed and a camera that captures a facial image of a person facing the display are used in the human-machine screen display method.
A distance detection unit that detects a distance between the screen and the face of the person, a distance determination unit that compares the distance and a reference distance value, a feature detection unit that detects a feature of a facial expression of the person, and an expression determination unit that identifies the expression are provided in the camera. A screen display enlarging unit is provided in the display. The screen display enlarging unit enlarges one of the screens facing the person using signals of the distance determination unit and expression determination unit.
In JP 2013-222356 A, “in the case that the characters or graphics displayed on the screen is too small to distinguish from each other, the screen is automatically enlarged by such typical, natural operation and expression that the face is brought close to the screen to squinch eyes, so that monitoring control can smoothly be performed while focusing on an object to be monitored” is described as an effect of the human-machine screen display method having the above configuration.
For example, JP 2011-118733 A discloses a PLC including a higher-level PC and a station that communicates with the higher-level PC. The station includes a plurality of modules including a CPU module. The higher-level PC includes a station monitor. The station monitor acquires running state codes of the plurality of modules through the CPU module. In the case that an alarm is generated, the station monitor refers to an alarm message file corresponding to the running state code, and displays an acquired alarm message.
In JP 2011-118733 A, “because detailed running states of various modules constituting a unit can collectively be checked on the higher-level PC side, the running states can be monitored on the PC screen without directly checking the real machine” is described as an effect of the PLC having the above configuration.
However, in JP 2012-208931 A, JP 2013-222356 A, and JP 2011-118733 A, the programmable indicator can hardly output the situation of the latest communication with the PLC in real time. This point will be described below with a communication error in the communication situation as an example.
Usually communication error is pop-up displayed in the programmable indicator or the PC. The pop-up display is continued until the user performs confirmation operation (for example, selection of an OK button). Usually the pop-up display is displayed after a certain period of time elapses since the communication error is generated. Accordingly, the programmable indicator can hardly output the situation of the latest communication with the PLC in real time. In addition, conventionally, the communication error that is of a history expressing an abnormality is not stored.